U.S. Pat. No. 5,034,837, to Schmitz, describes a rotary actuator type of disk drive employing a drive motor for powering the rotary actuator. The rotary actuator drive motor comprises a flat coil mounted on a coil support on the actuation. The coil moves in an arcuate path in a plane in a permanent magnetic field produced by a permanent magnetic structure. A magnetic actuator lock or latch comprises a latch pin on the coil support which moves in an arcuate path between opposed limit-stop surfaces on the stationary permanent magnet structure. The latch pin and limit-stop surfaces limit the angular movement of the rotary actuator and when the latch pin is in contact with either of the limit-stop surfaces magnetically latches the rotary actuator in that limit-stop position. Such limit-stop position, which secures the rotary actuator against rotary or angular movement, is the position occupied by the rotary actuator when the disk drive is not in use.
The rotary actuator arm structure, per se, is an integral part made of metal and comprises a pair of thin arms upon which the flat coil rides. The flat coil is secured to these arms by a bonding material stated to be a two part epoxy. The coil is wound separately, as a flat coil, and is configured in planform to fit the pair of arms. Diametrically opposite the coil support arms is an integral arm stack consisting of three axially spaced arms designed to receive, as by swaged connection, the mounting ends of respective load beams, the distal end of each of which mounts a transducer for scanning a surface of a disk.
Such an integral arm stack structure and load beam assembly is also seen in the patent to Coon et al, U.S. Pat. No. 4,829,329.
In the patent to Schmitz, the coil support arms being of metal are necessarily thin to avoid rotary actuator mass unbalance due to an overweight rotary actuator motor structure. This necessitates a close coupled coil moment arm which reduces the motor torque on the actuator. The actuator coil support arms being of metal present electrical insulation problems in mounting the flat coil. Mechanical instability may also be a problem especially in an environment where mechanical shock forces are high.
Structures of the type described by Schmitz and by Coon et al, while representing improvements in actuator design over earlier designs in achieving closer disk spacing, do not lend themselves to down size scaling to achieve disk drives of significantly less form factor.